Electronic devices, such as isolated integrated delta-sigma modulators (DSMs) and isolated amplifiers, employ DSMs that rely on internal bandgap voltage references to achieve relatively low temperature variation. For example, a product data sheet for an isolated amplifier may state that an isolated amplifier has a temperature gain drift of about ±15 parts per million per degree Celsius (ppm/° C.). To achieve a relatively low temperature variation, manufactures often trim the electronic device's internal bandgap reference voltages to a designated value. However, errors in the bandgap trimming process could negatively impact the temperature gain drift. For instance, a bandgap trim error of 1 millivolt (mV) could introduce a temperature gain drift of about 2.8 ppm/° C. Therefore, performing inaccurate bandgap trims can negatively impact the amount of temperature variation for electronic devices.
To account for package induced temperature shifts, manufactures generally utilize automatic test equipment (ATE) to measure and adjust internal bandgap reference voltages. One manner to measure the internal bandgap reference voltage for a packaged electronic device (e.g., an isolated amplifier) that has a relatively low package pin count is to connect the internal voltage to a suitable package pin (e.g., voltage input pin). One solution is to power down the analog front end and connect the internal voltages through resistors. Unfortunately, in certain instances, the assigned package pin may have a relatively large series resistance (e.g., greater than 1 Megaohm (MΩ)) between the assigned package pin and the signal-to-be-measured that causes measurement errors to be prohibitive when some small leakage current is flowing because of limited impedance of the measurement equipment. As an example, analog front ends in a differential amplifier configuration with relatively large bipolar input swings that exceed supply voltages typically need large input resistances to attenuate the input signal. The large input resistances can cause relatively large measurement errors when some small leakage current flows through the packaged electronic device's pin. Hence, being able to accurately measure internal bandgap reference voltages within packaged electronic device remains valuable in performing accurate bandgap trims and minimizing temperature variation for electronic devices.